This invention relates to mechanical pencils, specifically to a new internal lead advancing mechanism which pulls the lead to advance it instead of pushing the lead.
Conventional mechanical pencils require the writing process to be interrupted and the hand to change position for regrasping the pencil to enable the thumb to reach to and depress the eraser end three to four times to advance the lead to a desirable length for writing. The hand must then be repositioned to regrasp the pencil comfortably to resume writing. These conventional mechanical pencils are provided with an internal push-type chuck mechanism which is caused to push the lead to advance it simultaneously as the depressible end is depressed which necessitates the pencil to be lifted away from the writing surface to allow space for the lead to advance.
The applicant's invention is provided with a simple and unique lead-advancing device comprising of a plurality of equally opposing pivotally fastened spring-loaded spring clip mechanisms which, when activated by quickly applying and releasing slightly greater than normal writing pressure once to the depressible end against a writing surface, are caused simultaneously lift away from the lead, extend and regrasp the lead at a higher position then pull the lead to advance it to a predetermined length, suitable for writing with, during the contraction of the mechanisms to the their rest position.
The lead is caused to advance to a predetermined length equal to approximately three or four advances of a conventional mechanical pencil which is sufficient for writing yet short enough to reduce the chance of breakage during writing.
Thus a person can conveniently advance the lead to a predetermined sufficient length with a single push against the writing surface with slightly greater than normal writing pressure without ever changing the writing position of the hand and without interrupting the writing process.